1. Field of the Invention
The present invention relates generally to the field of power tools, and specifically to the field of vibration damping devices and support straps for power tools.
2. Description of the Related Art
In the landscaping and gardening industries, power tools are preferred over hand tools because of the increase in efficiency and productivity. Gasoline power tools, although more expensive to operate, are generally preferred over electrical tools because of the added mobility they provide, and because electrical power hook ups are not always readily available to a landscape operator.
FIG. 1 illustrates a power tool commonly used by landscapers. A leaf blower 100 includes a gasoline-powered motor 106 coupled to an impeller fan 108. The motor 106 and fan 108 are attached to a backpack frame 116, which is worn by an operator 110. The blower 100 includes a flexible section of tubing 118, which is coupled at one end to an output of the fan 108 and at the other end to an elongated rigid tube 102, which terminates in a nozzle 120. The nozzle 120 is generally interchangeable, with a variety of nozzle shapes available. A handle 104 is adjustably clamped to the rigid section of tubing 102 to allow the operator 110 to control the position of the nozzle 120. In some cases, the handle 104 includes throttle and engine cut-off controls. In other cases, no handle is provided.
When the leaf blower 100 is correctly positioned on the operator's back, the flexible section of tubing 118 is positioned under or slightly behind the elbow of the operator 110. The impeller fan 108 drives a stream of air at high velocity through the flexible and rigid tubes 118, 102, to be forced out the nozzle 120 in a focused stream. The operator 110 grips the handle 104 in his right hand 114 and, by moving his forearm, selectively positions the nozzle 120 to direct the stream of air. In the case where there is no handle provided, the operator 110 grips the rigid section of tube 102 to direct the stream of air. The operator 110 directs the focused stream of air to move leaves, grass clippings, or other organic refuse as required. A blower such as that illustrated in FIG. 1 may also be used as a power broom to sweep large surfaces, to move and collect litter, or to move light deposits of snow.
Because of the force of the air exiting the nozzle 120, the operator 110 is required to maintain a constant and strong grip on the handle 104 to direct the stream of air and to prevent the tube 102 and nozzle 120 from flying out of control. In gripping the handle, the operator's lower forearm muscles, which control the fingers, hand, and wrist, are in constant tension. Depending on the configuration of the blower in use, the wrist of the operator may be hyper-extended or otherwise awkwardly positioned as well.
A landscape worker may be required to operate such a device daily for many hours at a time. During operation, vibration of a significant amplitude is transmitted from the motor 106 and the fan 108 through the flexible section of tubing 118 into the rigid tube 102 and into the handle 104. Because the operator is required to grip the handle 104 with some force in order to direct and control the air stream passing out of the nozzle 120, there is a high degree of coupling between the handle 104 of the blower 100 and the hand 114 and arm 112 of the operator 110. This high degree of coupling permits the transmission of vibration from the tube 102 and the handle 104 to the hand 114 and arm 112 of the operator 110.
A significant problem for many professional landscapers is the effect of long term exposure to the vibration of tools like leaf blowers, grass trimmers, and brush cutters.
Recent research has linked certain occupational injuries with long-term exposure to vibrations caused by vibrating tools such as the leaf blower 100 of FIG. 1. As a class, these occupational injuries are referred to as vibration syndrome. Vibration syndrome includes such injuries as carpel tunnel syndrome and Raynaud's phenomenon.
Carpel tunnel syndrome involves the entrapment of the median nerve as it passes through the carpel tunnel located in the wrist. Compression of the nerve in the tunnel produces numbness, tingling, and burning sensations in one or more of the fingers of that hand. Carpel tunnel syndrome is associated with occupations that required repeated forceful, awkward wrist positions and the use of vibrating power tools.
Raynaud's phenomenon is characterized in its early stages by persistent tingling or numbness in the fingers. More advanced stages include blanching of a fingertip with or without tingling and numbness, blanching of one or more fingers beyond the tips, and extensive blanching of the fingers and the hand. Over time, Raynaud's phenomenon may result in decreased hand and arm muscle strength, and may cause persistent numbness and cold sensitivity. Raynaud's phenomenon is associated with extended exposure to hand-arm vibration such as from vibrating power tools.
There are several factors that will increase the risk of incurring vibration syndrome injuries: vibration frequency, vibration magnitude, exposure time, awkward and static postures, temperature, and tool design.